Fluid density measurement



April 7, .1942. R. E. IRWIN FLUID DENSITY MEASUREMENT Filed Nov. 16, 1938 2 Sheets-Sheet 1 )ll/Illll'I/llI/Il/ll/ I April 7, 1942. R. E. IRWIN FLUID DENSITY MEASUREMENT Filed Nov. 16,. 1938 2 Sheets-Sheet 2 situ density or specific volume of a fluid Patented Apr. 7, 1942 I UNITED" STAT FLUID DENSITY MEASUREMENT 1 RoyE. Irwin, Toronto, Ontario, Canada, assignor --to The British American Oil Company, Ltd.,

Toronto, Ontario, (kinda, a corporation'ot Canada ,Application-Novcmber16,1.938, a SerialNo.240,5 99% v 17 M 4 Claims. (01. 265-44) present invention relates generally to an apparatus for determiningthe properties or a fluid, and more particularly to an apparatus for continuously determining the in situ density or specific volume of a flowing fluid undergoing a change or conversion.

In the processing of flowing fluids,.it is frequently desirable for control purposes to have a continuous record orindication o! the in. situ density or speciflc volume of the fluid, without withdrawing a sample and determining its properties by means of a hydrometer, Westphal balance, or other laboratorymethods applicable to withdrawn samples.

of density or specific volume of a withdrawn sampie is a ditflcult and expensive operation in any case, and of little or no value as far as indicatingthe corresponding property of the fluid in its flowing condition, especially when dealing with fluids at temperatures and pressures which are materially different from atmospheric conditions. In addition, such cold sampling procedures are notapplicable for the determination .of the in situ properties of fluid mixtureswhich are not stable at atmospheric conditions. Thus, the mixture may be. rapidly-undergoing a change or'con- .ple would fail to indicate the density or specific volume of the fluid under the conditions obtaining in the flowing stream. Fortheseandother reasons, it is highly desirable to einplo'yan apparatus which is capable of reflecting thein situ density or specific volume of the flowing fluid stream. and thereby aflord a continuous indication or record of the fluid properties under actual flowing conditions. s j

One of the objects of thepresent invention is to provide an apparatus for determining the in under flowing conditions.

Another object is to provide anapparatusfor determining the in situ properties 'of a fluid Y undergoing a change or conversion while flowing in the form of a stream. V v

Another object is an apparatus for determining thein situ density or specific volume of a flowing fluid, which is applicable not only to liquids or gases or vapors, but also to mixtures thereof.

. r I The foregoing objects may be accomplished in 55 accordance with the present'invention, oneaspect of which includes an apparatus which continuously compares the weight per unitarea of a vertical column of a fluid, the density orspeciflc volume of which 1S 't0 be determined, with'the weight perunit area: of a column of astandard fluid of known density or specific gravity.

In order more clearly to disclose the natureof the present invention, reference is made to the'accompanying drawings wherein several illustrativeioiins of the apparatus contemplated by The periodic determination, 5

version with, the result that the character or the the I present invention 93i: diagrammatically shown. It should be unde tood. however. 3 that the present invention is'by ho means restricted to the embodiment hereinafter more particularly described, the drawings being merely illustrative of the principles involved.

Referring generally'to the drawings.

Figure 1 is a sectional elevation of a simple form of apparatus in accordance with"thepresent invention.

Fig. Z isan enlarged-sectional elevation showing 'a side view of a modified form of nipple;

Fig. 3 is an enlarged sectional elevation showing an endview of the modifledmipple of Fig. 2 in a changed position;

Fig. 4- is 'a sectional elevation of. a modified form of sealing pot.

Fig. 5 is'a front elevation ot-a modified aim of the invention'wherein a portion of the flowing fluid is by-passed-around an adjustable orifice.

Fig. 61s a further modified form of theinvention wherein a small auxiliary pump'is us alto responsive instrumentality.

Referring nowgenerally to a preferred embodiment of the present invention, the main stream of 'a fluidA is pumped orflowsthrough conduit i on which column. 2 is 40 shown as a vertical conduit through which a por- I tion of fluid A flowsat a rate-controlled byoutlet. valve- 3.v The fluid passing irom valve 3 maybe passed to waste, or returned to the process at. anysuitable point as desired. The rate of thefluid A at a thermocouple Q at approximately .the same temperature as that indicated at therflow through colunm 2 is, sufllcient to maintain mocouple 5,.10 cated in the main fluid conduit I.

The'velocity of flow through conduit 2 is maintained approximately constant by adjustment of valve 3 and at a suflicicntly'low rate to avoid iriction loss and the development or a substantial pressure differential between tap-off connectinglines 6 and 1. l

The opposite legsqoi a U'-tube or manometer Fig. 1 illustratingr l containing a sealing fluid Care connected'by 2,27a,2s4 I r o drop can'be minimized to a substantial degree, by controlling the rate of flow of the fluid thereconduits s and ill to the tap-oi! connections 6? g and I, a sealing means II and I2 being interposed between the conduits O and: Ill and the tap-off lines 8 and I. ifdesired. 1 The conduits 9 and II are fllled with a reference or standard;

fluid 2B,.fwhieh' has a known density-gor specific gravity; and which is preferably immiscible with on both sides of the U-tube or'manoineter I.

above the sealing fluid C, such as; mercury, for" with reference to a scale cll'is determined byfi the float' In, which rises and falls the level fthe sealing fluid changes in one .leg of the ma-- nometer or, U-tube.

- large diametergconduit. As shown .in Flg. 2,.-the

through and by employing a large, diameter conduit for-column 2. The modifledform oi nipple shown in Figs. 2 and 3 may also be employed to this end, either with or without the use of a ahead 2! ,of thenipple is ,bent to receive of thevelocity head. This velocity head varies substantially as the square of the velocity of flow, and the friction loss varies accordingly. It will tlierefore be seen that as the velocity of flow inexample. The position ofthe indicator arm, 1

to maintain the reference fluidB at: a" substanare maintained one heat exchange relation with vice ll, such as a temperature-responsive control device, well lmown, or throughtheagency of f, for esample, sat

the pressure is maintain.

was: medium? distinguished from speciflc gravity, it is necessary i creases,- fgiving a greater pressure drop between the ccollections',- the pressure at the upper connection, would likewise increase, thereby compensating for this'increase in pressure drop; ,As H shown inFig. 3, this nipple may be adjusted so a that the increase in velocity head may bemade to correspond exactly to the increase in pressure, I drop. With the nipple 2| pointing upstream, full velocity head will of course beattained., ,If, however,- thehip'ide is rotated, the per cent of jvelocityhead-would decreased so that at 90 a ;suitable medium sucnasifluidfor exam le, .i steam,-.iin' a jacket l6'.- "i'he control 0! this .tem-- peratureinaybereadily effectedbycontrol de- Temperaturecontrol 'is desirable if ftliefrefer ence fluid 13 is one which does nothave new temperature coeiflcient; If, however, the refer ence fluid has a zero temperature co-efllcient-of expansion, the temperature-controlmeans diargrammatically illustratedin the drawings: may beldispensedwith. a j

'Ihez prineipiesinvolved in the foregoing apparatus may be understood froin the following illustrative example: Assume a hat H is the bfj rias nqws'H modified fo'rm'ofthe apparatus which maybe used' where the main stream is fectiveheight of columns! and]; thatHAiisi I, a a, 4, a a

conducted through; avertic'al pipe I --at avelocity theiweight per unit area in equivalent inches of and ms is the weight per unit area in equivalent inches of water of fluid BinMP IJImh I for the heightH, When venting "valves l land II are 1 opento the, atmosphereiandithe valves II and 20 s :inw,the,tap:ofl lines 5 and,l ;are closed, the'derflectionof the columnofmercury C effected by sine static-,headoffluidgB; insthe twolegsof the Y uni-nanometer lis notediandgthe equivalent,=numberof inches of water equal to: this, ieflection may be determined. -When fvent valves] I and llrare closed, and'vaivesiltand 20 are opened, the difference in the'relationship of the fluids -in columns 2 and l. is also not iand this may be expressed 'inatenns of --inches of' water or per :cen'tof total scale deflection: onscale II by. pointthere would 'besubs'tantially no velocity head impressedionthe otheriiconnection. By flowing a fluid of constant "density through the pipe, but

at. dlflel'eiii; velocities, the nipple maybe adjusted so t aml s such change in veloltithe irecordingior indicatingqarm ll remainsjat the 7 correct freadinz'Q EIn this manner variations causedby friction'los'smay be overcome. illustratesa modifled form ofsealing pot 22 which'permitj the use of a'i'eferencefluid that is nisciblewith the fluidwhose density is to be determined; "sealing pot includes abel-' I lowsril'which eirpaiids and contracts as the' static head incolumn 2 varies witha change in [density "of ithe flowing fluid. "Fluid" A: enters through conduit 2l while fluidHB'flows iii-and out through conduit 25 as the .densityof A (m seswhich, however, {isjtoo great to give? accurate 1 "readingslbecausej-jpf friction 1m;- 'According to th is alternative t e" portion of the vertical stream isby-passed around an adjust; able ounce; 26 "in the main vertical conduit 2.

The adiustableoriiice is positionedito give I. \sufllcient pressure drop across a' restriction so that the fluidwill be 'causedtoflow through the by-pass 1a; at a rate adjusted by means ofd'he valve 21.; l'heflowof lthe fluid through-the by; ans in isn icated byfa now indicator, which] servesgasa basis for' resettingjthe valve 2'! when tthevrateo'f flow inthefby p'a'ss Iavaries from a predetermihed'jfflow. 'I'he'other-parts ofthe apparatus are substantially thejsain'e as those shown product of the density'of flu'idB and the ratio of HA toHB, or the per centof total differential.

It will thus be seen that as thedensity of the j fluid A v ch: nges, the relative position of indicator. a'rinjll reference to scale ll willcorre'spond I inglfch'ange thereby aflord ing a continuous indica'tioh of any variation (f n Figs. 2(andsis shownii'mbzimedh mf or; nipple whichniaybeused at the upper connec 1 tion to coi'npensatefor' pressure drop'due to fric- V nigpssiiowjia further modifled form crapperatus whichrnay be used wherethe main stream is ;conducted through a vertical conduit and the 1 velocity of flow therethrouchis high. In this iform ofthe apparatus, instead of using an ad-. a Justable oriflce'or valve in the main vertiealconduitflajsmalljauxiliary pump a is inserted i'njhe ,byssizaiwmaina nt en at ,0: n

in" the b'y-pass constant. {a'iheby pass'f conduit 2o corresponds to' the vertical:conduitfIfof-rig. 1. The other parts of the apparatuscorrespond 'to those sncwn in" m. 1-.

" scribed in the fore oins as mits the'continuous indication/of changes in the insitu density or specific volume ofthefluid'flowthe temperature of the main stream is substantially the same as that of the outlet of the vertical conduit, the in situ density of the main stream will substantially equal that in the vertical conduit. It will thus be seen that the apparatus provides a simple means of determining the in situ properties of a flowing fluid regardless of whether or not the main fluid'conduit is vertical or horizontal or in any given plane.

In the foregoing detailed description it is apparent that many variations may be made without departing from the spirit and scope of the invention. Thus, for example, as an alternative method of compensating for pressure drop where the main fluid stream velocity is relatively high. two meters may be employed, one being responsive to pipe friction drop compensating a second meter which is responsive not only to pipe fric tion drop, but also to the density or specific volume of the fluid. In this m'annerthe pipe friction drop may be cancelled out. Such a system of compensation is diagrammatically shown in Fig. l'wherein the manometer 421s connected to the horizontal outlet conduit by connecting lines 43 and 44, which are tapped into'said horizontal conduit by a distance equal to H. The pressure drop (if any) indicated by meter 42 will, of course, indicate pipe friction loss over the distance H, and since the meter 8 and its associated parts indicates the total diflerentialpressure due both to pipe friction loss over the distance H plus that due to the density of the flowing fluid, the second meter .42 provides the necessary information for correcting for any pipe friction losses. Many other variationsin detail will be apparent to those skilled in the art. I therefore intend to be restricted only in accordance with the following claims.

I claim:

1. The combination with avertical conduit for conducting a flowing fluid, the density of which. is to be indicated of a U-tube containing a sealing liquid, conduits connecting opposite legs of the U-tube to vertically spaced points. in said verticalco'nduit, a reference fluid'in said connecting conduits, indicating means positioned by and with the sealing liquid in one leg of said U-tube, and means for maintaining said reference fluid at a substantially constant temperature. V Y

- 2. The combination with a vertical conduit for conducting a flowing fluid; the density'of which is to be indicated, of a U-tube containing a sealing liquid, conduits connecting opposite legs of V the U-tube to vertically spaced point's'in said vertical conduit, means for preventing the fluid in said vertical conduit from entering said U-tube,

a reference fluid in said connecting conduits, in-

dicating means positioned by the height of the sealing liquid in one leg of'said U-tube, and means for controlling the temperature of the reference fluid.

3. The combination of claim 2 wherein said 4. The combination of claim 2 wherein said means for preventing the fluid in the verticalconduit from entering the U-tube comprises a sealing pot. 

